1. Field of the Invention
The present disclosure relates generally to a method for controlling slip of a continuously variable transmission (CVT), and more specifically, a method for controlling slip of a continuously variable transmission (CVT) which can enhance fuel efficiency by reducing loss of hydraulic power within a range in which slip does not occur, by decreasing clamping force of a primary pulley and a secondary pulley based on a control input torque of the primary pulley of a continuously variable transmission (CVT).
2. Discussion of Related Art
Generally, a continuously variable transmission (CVT) is advantageous in that it has a high efficiency because an operation point of an engine is close to OOL (Optimal Operating Line) over a conventional multi-step automatic transmission. However, the CVT is disadvantageous in that as the control pressure and friction loss are also high, its own efficiency is low and torque capacity is limited.
More concretely, transmission of the CVT can be performed as a rotation radius of the belt is continuously changed by axially translating a primary pulley and a secondary pulley while providing clamping force to the pulleys.
By the way, if the clamping force applied to the pulleys is greater than that required, excessive tension occurs on the belt, thereby shortening lifetime of the belt, as well as causing loss of hydraulic power required to generate the clamping force. On the contrary, if the clamping force is very low, a speed difference between the belt and the pulleys occur, thereby causing macroscopic slip resulting in loss of a power transfer function.
The related art of the present invention is disclosed in Korean Patent No. 10-1042064 issued on Jun. 9, 2011 and entitled “Continuously variable transmission operating method”.